FIG. 1 depicts a conventional method 10 for fabricating a magnetoresistive sensor in magnetic recording technology applications. The method 10 typically commences after a conventional magnetoresistive or tunneling magnetoresistive (TMR) stack has been deposited. The conventional read sensor stack typically includes an antiferromagnetic (AFM) layer, a pinned layer, a nonmagnetic spacer layer, and a free layer. In addition, seed and/or capping layers may be used. The conventional magnetoresistive stack resides on an underlayer, which may be a substrate.
The conventional method 10 commences by providing a conventional hard mask layer and a photoresist mask, via step 12. The conventional hard mask layer is typically a material such as SiC or diamond-like carbon (DLC). The conventional photoresist mask has the desired pattern, which is transferred to the conventional hard mask layer. The conventional photoresist mask covers the region from which the conventional magnetoresistive sensor is to be formed, as well as a portion of the transducer distal from the sensor. However, part of the device region adjoining the magnetoresistive sensor is left uncovered.
A conventional hard mask is defined from the conventional hard mask layer, via step 14. Step 14 includes transferring the pattern from the conventional photoresist mask, for example through a reactive ion etch (RIE). The photoresist mask may also be removed in step 14.
The magnetoresistive structure is defined, via step 16. Step 16 typically includes ion milling the transducer. Thus, the exposed portion of the magnetoresistive stack is removed. The magnetoresistive structure being defined may be a magnetoresistive sensor for a read transducer.
The hard bias material(s), such as CoPt, are deposited, via step 18. In addition, seed and/or capping layers may be provided in step 18. The hard bias material(s) and other layers are deposited while the conventional hard mask is in place. In addition, a shallow mill may be performed as part of providing the hard bias structure. A capping layer may be deposited after the shallow ion mill is completed. The capping layer typically includes a noble metal such as Ru, Ta, and/or Rh.
A chemical mechanical planarization (CMP) is performed, via step 20. This CMP aids in removing the hard bias materials above the hard mask and planarizes the top surface of the transducer. The hard mask may then be removed, for example via a reactive ion etch (RIE), via step 22. An additional planarization is performed, via step 24. The stripe height of the sensor is then defined, via step 26. Note that in some instances, the stripe height may be defined in step 26 prior to the steps 12-24 used at least in part to define the magnetoresistive sensor.
FIG. 2 depicts a conventional transducer 50 fabricated using the conventional method 10. For clarity, FIG. 2 is not to scale. A TMR sensor 54 residing on a substrate 52 is shown. Also shown are hard bias 56 and 58. The TMR junction 54 has a track width of w and inboard and outboard junction angles, α and β. The inboard junction angle, α, is closer to the center of the substrate on which the junction 54 is fabricated than the outboard junction angle β.
Although the conventional method 10 allows the conventional transducer 50 to be fabricated, there are several drawbacks. It is typically difficult to control the CMP performed in step 20. Thus, some portion of the hard bias materials 56 and 58 may be depleted of certain constituents, such as Co. It is also difficult to polish the desired amount hard bias materials above the small areas, such as the TMR sensor 54, while removing a sufficient amount of the hard bias materials in wider areas, such as the test area guide (not shown). Conversely it is difficult to remove the desired amount of the hard bias materials from wider regions without overpolishing narrower areas. Further, the slurry used for the CMP performed in step 20 may result in corrosion of underlying metal layers, particularly Co depleted hard bias materials 56 and 58.
Accordingly, what is needed is a system and method for improving the fabrication of a magnetic recording read transducer.